Serie A leaders Inter Milan squeezed into the quarter-finals of the Italian Cup on Tuesday, winning 5-4 on penalties after being held 0-0 after extra time by third division Pordenone.

Japanese defender Yuto Nagatomo nailed the winner from the spot after 120 minutes of frustration at the San Siro as home goalkeeper Daniele Padelli saved two penalties to put seven-time winners Inter through to a showdown with either AC Milan or Verona, who play on Wednesday.

Luciano Spalletti's decision to overhaul his squad after last Saturday's goalless draw against Juventus backfired against the spirited Serie C side from near Venice who eliminated top-flight Cagliari in the last round.

"The players who have played less found it difficult tonight, because Pordenone had quality in midfield," said Spalletti.

"We couldn't take control of the ball to play, we felt challenged instead of everyone dealing with their various roles, and then from a psychological point of view everything became complicated because they became fired-up as the game went on.

"We were below our potential. At the end I was starting to lose confidence."

Spalletti left big guns including captain Mauro Icardi and Ivan Perisi on the bench bringing in defender Andrea Ranocchia, forward Yann Karamoh, and reserve goalkeeper Padelli.

Karamoh, 19, let two chances slip by before being substituted by Perisic, with an increasingly frustrated Spalletti sending in Serie A top-scorer Icardi late in regular time.

But even the Argentine star couldn't break through as he headed over crosses from Portuguese Joao Cancelo and Perisic, leading to the penalty shoot-out, in which Nagatomo scored the final penalty to seal his side's passage to the next round.

"Everyone had their heads down in the dressing room, and I understand that," said Pordenone coach Leonardo Colucci.

"They have to remember that we only lost on penalties to the Serie A leaders. Taking Inter to penalties is like winning the Cup for us."

The Italian Cup last 16 matches will be played throughout December and include six all top-flight clashes, including Napoli against Udinese and holders Juventus against Genoa.